I want add-on SD card reader/writer/slot/controller in my raspberry pi so that i can keep OS separate from my program. Primary SD card will load OS and work normally and program & data will remain available from add-on card. Please suggest
a) what good hardware extension or component available as add-on card for raspberry pi 3b
b) suitable software available.
OR if i can use USB Pendrive directly because i have USB slots spare. How?
Please note: 1) I am not talking about increase SD card size and 2) not talking about creating separate partition on first SD card.